Thermoelectric generator and burner therefor



P. L. DULANEY THERMOELECTRIC GENERATOR AND BURNER THEREFOR Jan 6, 1942.

Filed Aug. 8, 1939 2 Sheets-Sheet i 015 1.z Lo

Amveaes I \m/wnbr DnuL L. DuLaNEY WW7 Rkkornzyg,

' Jam, 6, H942. P. 1... DULANEY THERMOELECTRIC GENERATOR AND BURNER THEREFOR Filed Aug. 8, 1939 2 Sheets-Sheet 2 A it 0m an y MQJX MW Patented Jan. 6,1942

UNITED STATES PATENT OFFICE THEEll/IOI'ZLECZIERIG GENERATOR AN BURNER THEREFOR Paul L. Dulaney, Cincinnati, Ohio, assignor to The Huenefeld Company, Cincinnati, Ohio, a, corporatlon of Ohio Application August 8, 1939, Serial No. 289,010

Claims.

' closure of this alloy and the manner in which it operates will be given hereinafter.

It has been found in practice that, when the heat applied to the hot junction formed between the alloy and the connecting metal strip is obtained from the usual sources of heat, such as ordinary oil burners in which the fiameactually contacts with the hot junction, the electrical output of the alloy is subject to considerable variation. It has further been found that, when a number of thermoelectric units formed of the alloy are connected in series and the flame of the heat source is permitted to contact directly with the hot junctions, the latter are not heated evenly, either over their respective surfaces or as between units. Thus, one unit is heated to a far greater degreethan another unit, and the output of the generator is reduced accordingly.

The lack of control over the direct application of heat through permitting the flame to contact the hot junctions of the generator created a hazard to the generator of over-heating and seriously damaging the generator units. The alternative is to keep the average temperature so lowin avoiding uncontrolled over-heating that the effective gradient could not be maintained.

In accordance with my invention, I have discovered that unusually good results are obtainable in connection with the thermoelectric generators when the hot junctions are subjected to radiant or indirect heat. In following out this discovery. 1. have also invented an improved burner by which these results are obtained. This burner has broad application to the heating field, although as stated hereinbefore, it is particularly well adapted to provide heat evenly to a large number of thermoelectric units.

Accordingly, the primary object of my invention is to provide an improved burner which depends on oil for fuel and radiates heat evenly over a relatively large proportion of its heatemitting surface; to provide an improved oil burner of cylindrical configuration which radiates heat at a uniform intensity in radial directions; to provide an oil burner which operates eiliciently and is adapted to provide heat at exceedingly high temperatures even when using low grade oils.

The final and more specific object is to provide an improved burner which finds a particular adaptation to the'art of thermoelectriclty in that it furnishes heat of an indirect or radiant character for efficiently generating thermocurrents.

The invention will be better understood when reference is made to the following description and the accompanying drawings, in which- Figure l is a cross sectional view of a pair of thermoelectric units, to which my improved burner finds particular adaptation.

Figure 2- is a diagram indicating the manner in which voltage is measured between three of the thermoelectric units when heated in accord= ance with the principles of my invention.

Figure 3 is a graph showing the electrical out==- put actually obtained from of the units shown in Figures 1 and 2 when connected in se ries and heated by my improved burner.

Figure 4 diagrammatically indicates "Mia manner in which the improved burner operates to produce improved thermoelectric efiects when the thermoelectric units are arranged in a cylindrical configuration.

Figure 5 shows a cross sectional view, partly in elevation of an improved thermoelectric generator as described in the Wiegand application referred to hereinbefore and employing the improved burner which forms the subject of the present invention.

Figure 6 is a fragmentary view, somewhat diminished, taken along line 6-6 in Figure 5 to show the plan view relation between the improved burner and the thermoelectric generator.

Figure 7 is a fragmentary view on a reduced jecting in the same direction. It will be understood, in practice, that the units I are placed close together and are insulated from one another by means of a strip of mica, indicated at 2, placedbetween the segments. However, the

latter are electrically connected together by means of a metal strip 3 which is secured in any suitable manner to the outer surface of each segment and to the inner surface of the next ad, jacent segment. Thus, the segments are con-. nected in series and currents generated therein by heat applied to theharrow end or hot junction can be taken off from the terminal strips 3.

It was pointed out in the Wiegand application referred to hereinbefore that the units i may be composed of an alloy of antimony and zinc with the antimony in the percentage of approximately 67% to 55% and the zinc approximately 33% to 45% by weight (assuming the alloy to be 100%) with five to ten ounces of dechlorinated salt per hundred pounds of antimony and a trace of arsenic. The strip 3 may be constituted of any suitable metal having a melting point higher than that of the alloy of the unit 0, but in order to withstand corrosion at high temperatures, a metal called copel is preferred for this purpose. Copel is somewhat similar to German silver and is constituted of approximately 46% nickel and 54% copper. The metal in strip form is readily procurable on the market.

To give specific examples, it has been found that, when the units 5 are formed of a segmental block having a width at the narrow end of approximately %"'and at the wide end of approximately and a length of approximately 1%" and a thickness of approximately by heating the hot junction end of the block. to

approximately 800 F. and cooling the opposite end to approximately 200 F., it is entirely-possible to. obtain a voltage of one-tenth of a volt between conductors 3.

It was brought out in the Wiegand application that, when thirty segments of this size were connected in series to form a cylindrical layer and five such layers were provided, all connected in series, electrical energy depicted by the chart (Figure 3) was readily obtainable. Thus, at one ampere, the voltage was approximately seven volts. and at two amperes approximately four volts. It is apparent that this output is of a commercial magnitude and finds manyuses in the electrical art, for example, the energization of the heater or filament of radio tubes, charging storage batteries, operating electrical devices, etc.

As shown in Figure 1, the end of the block opposite from" the hot junction end is preferably cooled by means of a strip of copper 4 which is bent at the middle as indicated at 5 and is secured in any suitable manner to that portion of the copel strip 3 which abuts the wider end of the unit 8. length to form a pair of legs, as indicated at I, which overlap one another and can be spotwelded together and also to the upper flat portion of the copel strip. The latter may be secured to the unit in any suitable manner, for example. one or two vertically disposed tabs 1 provided at leach end of the strip and cast into the alloy.

In addition, the strip may be provided with a bent leg 8 which is also cast into the alloy. A mould may be provided and the strips 3 positioned at each end of the mould and the alloy poured Into the mould at a proximately 1350" F.

and allowed to solidify. Thus. the heat-radiating fin d and the copel strip 3 are rigidly secured to the unit 8 It has been found that the strip 4 can, when properly designed, radiate suificient heat to maintain the cold junction end of the unit atapproximately 200 F. when the hot junction end is heated to approximately 800 F.

The strip 5 maybe of suflicient when the units are spread out, as indicated in figure 2, instead of being arranged in an abutting relation, it may be desirable to provide between the lower ends. of the units a metal heat baffle 9 to prevent the heat from striking the sides of each unit. As a result of numerous tests,

it has been found that, when-the source of heat strikes the hot Junctions of each thermoelectric unit, deleterious effects are produced not only by 10 way of a fluctuating voltage as measured by the voltmeter l0, depending upon the irregularity of the heating source, but the electrical load is not divided equally among all of the units, since one of the hot Junctions may be heated to a higher 1.3 temperature than another hot junction. Indeed,

even parts'of each hot junction may be heated to a greater or less degree than other parts of the same junction. It is entirely possible to heat limited portions of the alloy or the connecting 20 strip to their respective melting temperatures without obtaining the maximum thermccurrent output from the unit.

in accordance with the present invention, I

have discovered that unusually good results may 2: beiobtained by way of large thermocurrents and voltages and greater operating life of the alloy and the copel strips when the source of heat is not permitted'to contact with the hot junction. There is, therefore, interposed between the Bunsen burners II- and the hot Junctions l2 of the units a metal heating plate l3 on which the flames H strike. The, plate, therefore, becomes heated and serves to distribute its heat uniformly over all of the hot junctions l2 and over every 33 part of each hot junction. Thus, the latter are -subjected to radiant heat, as indicated by the uniformity of lengths of the arrows shown at l5. -Notwithstanding the inter-position of the plate it, it is entirely possible to heat the hot junctions 82 to any desired temperature less than the melting temperature of the alloy and to maintain such a temperature throughout the hot junctions.

It was pointed .out hereinbefore that the thermoelectric generator may comprise thirty or more thermoelectric units in abutting relation and connected in series to form a circular layer. Any number of such layers may be connected in series to constitute the generator and, as illustrated, on there are five such layers. The typical characteristic shown in Figure-3 gives a general indication as to the power output of such a generator when the units are subjected to a temperature gradient of approximately 600 F., although it 5:, will be understood that considerably greater power output may be obtained when this gradient is increased. The layers are separated from one another by an insulating plate l8 (Figure 5). preferably of asbestos, spun glass or mica and go there is a similar plate I! at the upper surface oi the uppermost layer, also at the lower surface of the lowermost layer. On the outside of the plate I], there is a, metal plate II. The plates I! and I8 are of a diameter sufliciently 05 large to accommodate four or more equidistantly spaced bolts l9 provided with nuts 20 which serve to clamp the two metal plates l8 and, therefore. to hold all of the thermoelectric layers and the individual units thereof rigidly in place. The in bolts are insulated from the alloy by means of a lava tubing 2|. The plates l6, l1, and 18, also the hot Junctions of the thermoelectric units I. when assembled, have the some inner diameter. thereby defining the interior surface of a 3- cylinder.

For heating the inner surface of the hot junctions of the thermoelectric generator, there is provided a double-walled burner improved in accordance with my invention. This burner is constituted essentially of an enclosure 22 termed an oil bowl and having a U-shaped cross section, i. e., open at the top as indicatedat 23, and closed, at the bottom as indicated at 24. The bowl is supported on a conduit or pipe 25 which leads to an oil reservoir- (not shown). The interior of the pipe 25 communicates with the interior of the oil bowl 22 at two diametral positions .illustrated by the openings 26. A cylindrical lighting ring 21 of interwoven asbestos strands is contained within the bowl 22 and supported from the closed end 26 thereof by means of a wire truss 28. This truss preferably made in the form of loops stapled to the lower end of the lighting ring rests on the lower or closed end of the oil bowl. The lighting ring 21 has a length as measured in the vertical direction of the figure considerably shorter than the length of the bowl 22 and the upper end extends just beyond the annular opening 23.

The outer wall of the bowl 22 terminates in a flange 29 and the inner wall terminates in an inwardly extending rolled flange 3t. There is an apertured cylinder 3| loosely resting on the flange 29 and, therefore, removable in order to apply an igniting torch to the upper or lighting edge of the ring 21. The apertures in the-cylinder 3| are indicated at 32. The cylinder extends to a height preferably just above the third layer of the thermoelectric units.

There is an inner cylinder 33 having apertures 35 and arranged concentrically with the outer cylinder 3|. The inner cylinder rests on the flange 30, to which it may be secured. The upper end of the cylinder 33 is closed by a top piece 35 welded or otherwise secured to the cyl-' inder. The latter is also provided with three or more transversely extending partitions 38 having openings 31, arranged in a circular path, as can be seen more clearly in Figure 6. The inner cylinder 33 is pressed against the flange 30 by means of a threaded bolt 38 provided with a wing nut 39. The bolt is secured at the end opposite from the nut to 8. lug #30 which may be welded to the conduit 25. The pipe or conduit 25 may pass through a hand-operated valve (not shown) of any suitable type, to, a reservoir (not shown), containing a hydrocarbon fuel such as kerosene. Thus, oil is fed from the reservoir and controlled by the valve to the openings 26.

Prior to the lighting of the burner, the oil fills the annular space between the lighting ring and the bottom of the oil bowl 22, the level of the .oil reaching a position "As" to 1" up from the lower surface of the lighting ring. After the ring 2'! has been lighted by removing the outer cylinder 3i and applying a torch, the level of the oil automatically drops, provided the oil valve has the proper setting, to a position just below the lighting ring, as is indicated in Figure 5. The supply of oil is controlled in such a manner that the zone of greatest combustion is positioned fairly low in the annular space between the cylinders 3!, 3 8. Thus, the flame is kept relatively low and the burner is operated at less than its maximum capacity. 7

However, the flame will extend upwardly between the walls 3!, 33 to a-distance practically as high as the upper surface of the upper layer' of the generator.

The oxygen for combustion is obtained from the air which passes through a number of openings 4| positioned about a cylinder, on which the bottom plate l8 rests, as indicated at 42. This air flows through the openings 32 in the cylinder 3| and also through the openings under the bowl 22, passing upwardly through each of the openings 31 and into the inter-cylinder space through the openings 34. A draft or chimney effect introduced by the openings ll, 32, 31 and 34 is such as to cause the flame to emerge at the upper end of the burner as an annular jet. following the original direction and, therefore, spaced from the inner surfaces of the thermoelectric units 1.

In order to insure that the upper end of the flame does not tend to strike the thermoelectric units directly, it may be desirable to provide a so-called outlet ring 48 placed above the burner and supported on the plate It in order to retard and direct the products of combustion. This ring carries a wire safety guard 4'7. The ring, therefore, controls the amount and distribution of radiant heat reaching the two upper layers in the same manner as the vertical position of the outer cylinder 32 with respect to the three lower layers controls the distribution of radiant heat transferred to the lower layers.

In Figure 5, the flame is indicated by the curved lines 43 which, as will be noted, extend a considerable distance beyond the top piece 35. Figure 7 shows the manner in which the outlet ring 46 operates to converge the flame inwardly at a position above the uppermost thermoelectric layer, thereby directing the flame away from this layer but permitting the radiant heat to reach the latter. The vertical dotted lines 44 shown in Figure 5 indicate the direction taken by the kerosene vapor on leaving the oil bowl and passing upwardly through the narrow annular spaces between the lighting ring and the bowl. It will be noted that the lines at extend for considerable distance upwardly from the top edge 23 of the lighting ring, indicating that the flame does not extend as far down as the lighting ring.

The ample and constant supply of oil in the burner bowl to the proper level, combined with the proper heating of the lower walls of the combustion chamber and the upper walls of the oil bowl combine to supply a uniform supply of oil vapor into thecombustion chamber. The annular space at the bottom of the bowl containing free oil which makes possible a constant and ample evaporation of oil taken up by capillary action of the ring and the cooler walls of the bowl because of this constant evaporation, prevent the permanent deposits of carbon on the ring which formerly occurred. The coating of the ring with baked on free carbon or asphaltum residue, is thus eliminated.

The feature of spacing the lighting ring from the bottom of the oil bowl 22 by means of the truss 28 is described and claimed in the Dulaney application Serial No. 39, 1, filed Au ust 3, 1939, and entitled Lighting rings for wickless burners.

In order to assure that the flame within the burner is of uniform, .intensity over the entire height of the thermoelectric units, the spacing and size of the openings 37, also the distances between the partitions 3%, and between the top piece 35 and the upper partition 36, are so determined, preferably by experiment, as to provide the proper gradation of air through the openings 86. Thus, the supply of oxygen is regulated at the different levels of the burner, as represented by the openings 36 to provide a flame of uniform.

to strike'the'units. I

4 intensity throughoutthe length of the burner,

' whichinturn causes an even application of heat I larity in the flame.

is so marked that, in the case of the thermoelecto the-interiorsurfaceof the thermoelectric generator,- -i lhagnarrow annular space between the d theinterior surface of the thermoegulates orcontrols the amount of 'air on the sizeof the burner, the size of the openings 32, the annularwidth of the combustion I chamber and other factors.

The outer wall 3!, in addition to constituting i apart of the combustion chamber, also serves offodoriierous fumes or producing any irregu- Its economy of operation 1 tric generator referred to hereinbefore and progenerator' also constitutes an air flue in I and, refore, oxygenpassing through the open- 1 lugs- 32 at the difierent levels throughout the burner. ,This flue space is,therefore, preferably accurately determined by experiment and depends ducing the energy shown in chart form in Fig- I ure 3, a gallon of ordinary gasoline will last the burner from twenty-six to thirty hours, raising the temperature of the generator hot junctions to the required amount with less than .04 gallon per hour.

While I-haver explained my invention more particularly in connection with the improved I thermoelectric generator which forms the.sub-,

to'preventthe flame from actually impinging on I I the thermoelectric unitsand'tends to smooth out still further anyslight irregularity in the flame within the burner.

It is conceivable that, in the absence of the wall 31,-the flame may have such I lengths. Thus, the'hot junctions of the thermoelectric units i are subjected to'heat of uniform I intensity,-not only asibetween junctions,but also I over every portion of each juncti0n= Itis apparent that thevoltag'e generated under these nquiredand complete absence from fumes and ject of theWiegand application referred to hereinbefore, it is to be understood that the invention is not limited I to this. particularapplication. \Indeed, the improved burner finds utility I in any case where a heat source of uniform intensity: lsrequired, and in which the burner is operated with a low flame and, therefore, at I y I less than its maximum capacity withconsequent optimum economy The improved burner makes a valuable contribution to a laboratory requir y I ing a heat source of even temperaturewherein the; only fuel or energy available is oil. The

burnermay also be used in household furnaces I and stoves, where economy of operation is rea disagreeable odors.

conditions is of an optimum value and is much u more constant than if the flame were permitted a In the absence of wall 3!,- it

.sible to sustain a flame reaching upward along the generator wall as introduction of air throughout the entire height of the flame is necessary from both inside and outside the annular combustion chamber. With air introduced only from would be impos 1 It will be understood that I desire to comprehend: within my, invention such I modifications as come within the scope of the claims Having thus fully described myinvention, what I claim as new and, desireto secure by Letters Patent is: I I

1. In combinations generator :tive force comprising a plurality of thermoelectric units electrically connected'together to the inside, the outer surface-generator face would be coated with carbon and the flame would sink to the base of the combustion chamber, where a small portion of air could be had from the outside below the generator wall. The wall 3! is an essentialto all wlckless burners and particularly to; thisone where a uniform heat is desired throughout the entire heighth of the combustion chamber. 1

In addition, the uniformity of the radiated heat permits the hot junctions to be heated up to their maximum temperature without the dangel of localized melting or otherwise deleteriously afiecting any portion of the junctions. Not: withstanding drafts or other irregularities of the air travel through the openings H, the voltage remains substantially constant under load for any given current output, this result being directly attributable to the uniformity of heat radiation and distribution by the wall 3|, as indicated by the arrowed lines 46 of equal length in Figure 4.

It has been pointed out that the openings 31,

3d and 32 together with the air flue effects all tend to cause the flame within the burner to burn uniformly. This uniformity of combustion is I form a layer with the hot junctions adjacently positioned said generator consisting of a plurality of said'layers stacked on one another, and means including a double-walled oil burner to form a combustion chamber, said walls enclos-- ing the flame for heating the hot junctions uniformly and extending over only a portion of the hot junctions, all parts of the burner being spaced from the hot junctions, and means including a draft-directingring secured to said generator for directing the flame away from the remainder of the hot junctions or in heat-radiating relation therewith.

2. In combination, a generator of electromotive force comprising a plurality of thermoelectric units electrically connected together to form a layer with the. hot Junctions adjacently positioned, said generator consisting of a plurality of layers stacked on one another, and means in--' eluding an oil burner for heating the hot junctions uniformly, said burner including an oil flame contained between a pair of concentrically arranged cylinders contained within said layers, said cylinders extending over only a portion of the inner surface of said layers, and a cup-shaped element secured to the upper portion of the generator and mounted over said flame for directing the flame away from the upper layers of the stack but permitting the flame to remain in heat-radiating relation therewith.

3. In combination, a generator of electromative force comprising a plurality of thermoelectric units electrically connected together to form a layer with the hot Junctions adiacently positioned, said generator consisting of a plurality of layers stacked on one another, and means including an oil burner for heating the hot juncof electromo- I aaeaas'r flame positioned near one of the layers, and

hotjunctions but permitting the flame to remain in heat-radiating relation therewith.

4. In combination, a generator of electrometive force comprising a plurality of thermoelectric units of segmental configuration and electrically connected together to form a cylindrical layer with the hot junctions positioned around the inner diameter of the cylinder, a plurality of said layers stacked one on the other to form an elongated cylinder and electrical connections between the layers, means contained within the cylinder for heating the hot junctions uniformly, said means comprising an oil burner having an annular flame positioned near one of the layers,

and means for preventing the flame from contacting any of the hot junctions, said last-mentioned means including a double-walled perfoerator for directing the flame away from the remainder of the hot junctions but permitting the flame to remain in heat-radiating relation therewith.

5. In combination, a generator of electromotive force comprising a plurality of thermoelectric units electrically connected together to form a layer with the hot junctions adjacently positioned, said generator consisting of a plurality of said layers stacked on one another, and means including a double-walled oil burner to form a combustion chamber, said walls enclosing the flame for heating the hot junctions uniformly and extending over only a portion of the hot Junctions and all parts of which are spaced from the hot junctions.

PAUL L. DULAN-EY. 

